Logical switching systems



. April 2l, 1970 v H. SCHMIDT I 3,507,122

LOGICAL swITcHING SYSTEMS Filed sept. 11. 196s4 FIG 1 x INVENTOR I--l United States Patent O U.S. Cl. 61-45 5 Claims ABSTRACT OF THE DISCLOSURE A logical switching system serving more especially for the control of roof support frames or props of hydraulic longwall support arrangements in underground mineworkings, by means of which switching system a plurality of operations that are independent of each other are segregated with respect to each other by gate units each comprising an erasure-dominating storage device, an OR element connected in front of the erasure input of the storage device and two AND elements connected to each of two unconditional outputs of the storage device. The cuttingoff of one operation can be effected by the erasure of the signal that initiated the operation, or it may be cut off upon the termination of the operation by means of a response signal indicative of such termination.

FIELD OF THE INVENTION (a) Background This type of switching system, regarded generally, has the purpose of grading in order operations which are alike or which differ from each other. This grading in order may consist, inter alia, in causing a certain operating procedure to complete its working cycle before one or more other operating procedures are initiated and at the same time in maintaining a definite sequence in the working cycles of these subsequently actuated operating procedures. In the case of hydraulic longwall support arrangements, the matter under consideration as regards the operating procedures may well relate to the working cycles of identical control chains appertaining to individual roof support frames or props. In underground mine-workings, however, the grading in order of dissimilar operating procedures in the above context, i.e. in the case of a self-advancing longwall support arrangement consisting of several normal frames and also some special frames (which in contrast to the normal frames fulfill the supplementary task of aligning the conveyor), is a more complicated matter.

(-b) Prior art To fulfill such purposes, up to the present time sequentially operated switching systems which function, for example, according to time or pressure patterns have been employed. The development of a hydraulic longwall support arrangement aimed at complete automatization demands an increasingly large number of possibilities of handling information in the system formed by the longwall support arrangement. Apart from this, this system must be combined with other systems in the longwall working, such as the systems made up of the coal-stripping appliance, of the conveyor and of the self-advancing mechanisms, all this being within the framework of future developments. Still more far-reaching combinations, which also involve in the switching system further systems in other galleries under exploitation, would appear not impossible. The switching networks required in such circumstances, With their multiplicity of problems relating to cut-off techniques, can no longer be produced with the se- 3,507,122 Patented Apr, 21, 1970 quentially operated switching systems hitherto employed.

In other branches of technology, switching systems consisting of connection and storage logic devices have already been introduced, A hydraulic longwall support arrangement which has automatically advancing support units and in which the cut-off problems are solved within a logical switching system by the formation of changing groups constitutes a prior proposal not yet belonging to the state of the art (German patent application B 92,993).

The building up of switching systems with connection and storage logic devices requires considerable expert knowledge, however, In mining there is the additional requirement that already installed switching systems should be capable of alteration, in case this becomes necessary because of change in operating conditions. On this matter, one must proceed from the premise that such alterations are more frequently required than in other spheres and must be carried out by personnel having only limited qualifications.

At the basis of the invention is the technical problem of building up the required gating circuits in so simple a manner that they can be easily brought into being even |`by people having limited qualifications in the field and, when necessary, without a more fundamental knowledge of control techniques, even with the most complicated logic being involved.

BRIEF SUMMARY OF THE INVENTION In accordance with the invention, this problem is solved by the provision of gate elements which can be switched inter alia, are identical with each other and in themselves constitute basic blocks of a switching system, more especially a pneumatic switching system, which gate elements in each instance comprise an erasure-dominating storage device in front of whose erasure input an OR element is positioned and whose two outputs are each positioned at the inputs of two AND elements to constitute at least four conditional outlets of the gate element, but which in addition themselves each constitute an unconditional outlet of the gate element.

The gate elements may be switched in sequence in a variety of ways, and then constitute so-called gating groups. According to the position of the individual gate elements in the group and according to the number of the groups existing, various priorities result for the operating procedures controlled by the gate elements.

Since solely the gate elements, but not the basic elements comprised in them, need to be switched, inter alia, any desired control system involving gates can be produced -by but scantily trained personnel within a brief period of time according to a unit construction principle. The similarity of the blocks makes inexpensive production possible, and provides an opportunity to have the gate elements constantly available with the aid of a simple and economic stores system. In this way, dates of delivery in industry can be adhered to, and undesirable delays caused by these can be excluded. In particular, it is an essential feature that, by replacing individual gate elements, defects in the overall system which is controlled by the switching system can be very easily identified and eliminated.

DRAWING TITLES FIGURE 3 shows the design of a gate element according to the invention;

FIGURE 4 shows a symbol for the gate element according to FIGURE 3, and

FIGURE 5 shows the switching arrangement of gate elements according to FIGURES 3 and 4 in one gate group.

DESCRIPTION OF EMBODIMENT The -basic constituent of the gate element to be explained hereinafter is the erasure-dominating storage device reproduced in FIGURES 1 and 2. It possesses the features of two inputs I and N, and one or two outputs X, The output signal of a second output is always the opposite of the first output.

If a brief signal arrives at the information input I, then a signal is also produced at outlet X of the storage device. This signal is fed back to the parallel input of I on the upper OR-NOT element, and there replaces the information signal, as a consequence of which the information may be stored for as long as may be desired, even after the disappearance of the signal at I.

If an erasure signal appears at the erasure input N, then the feed-back is interrupted and the output signal X is erased. If the signals arrive simultaneously at both inputs I and N, the erasure signal will dominate. Then the information signal at I will not be accepted.

This erasure-dominating storage device constitutes the principal item of a gate element which will be described hereinafter.

As is shown in a switching system which will be explained in greater detail hereinafter as one example of an embodiment, erasure signals from various other gate elements affect the one gate element. Therefore, in front of the erasure input of the storage device there is interposed an OR logic element which collects all the erasure signals. In the embodiment shown in FIGURE 3, the subject under consideration comprises three OR inputs N1, N2` and N3.

The two output signals X and can be transmitted directly onwards, but their transmission onwards is also dependent upon conditions. This is rendered possible by four AND elements with outputs Y, Z, The stored output signals located at the inputs of the four AND elements are only transmitted onwards via the outputs Y, Z, Y., if the second input in each instance of the AND element-hence one of the inputs Sy, Sz

S; and Sz carries a signal. The outputs Y, Z, Y, are therefore conditional outputs of the gate element. Outputs X and are, on the contrary, unconditional.

To the inputs Sy, SZ

S; and Sz of the AND elements there may be connected any desired logic networks which for their part determine the conditions.

A simplied illustration of the gate element described hereinbefore and reproduced in FIGURE 3 in full detail is shown in the symbolic block diagram of the gate element in FIGURE 4. In FIGURE 5, the block diagram of the several gate elements there reproduced is still further simplified in that all inputs and outputs not required in a special case are omitted.

Within the scope of a switching system which is built up of identically formed gate elements described hereinbefore, the special gate element is denoted by two subscripts, generally by Vkp, the subscripts k and p describing the position of the element in the switching system. This will be explained in greater detail hereinafter.

A gate element Vkp of this type possesses the following properties:

(1) A signal at I appears at the unconditional output X and is stored until an erasure signal appears at at least one of the inputs N1, N2 The output X will then receive no signal. If there is simultaneously a signal at I and at one of the inputs N1, N2 then X will again 4 carry no signal. The unconditional output X' will only carry a signal when X carries no signal.

(2) The conditional outputs Y, Z carry the same signal as X when there is a signal present at the associated control inputs Sy and SZ. If this is not the case, then Y or Z respectively carry no signal. The same thing holds good for the conditional outputs Y and which are associated with the unconditional output having the control inputs S; and S;

Hereinafter will be found some examples of embodiments of switching system which are made up of a combined switching system of identically formed gate elements.

The first step towards obtaining a switching arrangement consists in connecting in series a plurality of gate elements. For this purpose., the output X or the conditional output Y of one element is connected to the input I of the other element. In special but rarer cases, the negative outputs or Y may also be employed. Because of the very great number of possibilities as regards combinations, only the more usual circuits will be described.

This connecting in series of a plurality of gate elements results in a functional group called a gating group. At least two gating groups must be present in a single control system involving gates. The first subscript k in the indexing of Vkp for a gate element indicates the gating group concerned. The applicable formula is therefore:

The second subscript p indicates the ordinal number of the gate element in the group k. The applicable formula is therefore:

If one proceeds from the concept that all gating groups are placed adjacently to each other, then there results a matrix-type arrangement of the gate elements. A gating group k therein occupies the k-labelled column. In the p-labelled row of the matrix the p-labelled elements of all the gating groups are located.

The row appertaining to the subscript p may be called the priority level p. Since in the completed switching system each gating group is associated with one of the operating procedures requiring to be controlled, the designation Vkp indicates the following:

The object under consideration is the gate element which is located in the k-la-belled gating group (of the operating procedure k) on the p-labelled level of priority.

The counting of the priority levels should be cornmenced from that side of the matrix at which the control signals arrive.

The second step towards obtaining a switching arrangement consists in conducting the cut-oit signals to the erasure inputs N1, N2, etc. of Vkp. Two types may here be distinguished, namely cut-off signals which originate in the same gating group, and signals which are fed in from another gating group.

The erasure signals originating in the same gating group have, apart from special cases, the following task:

- Immediately a gate element Vkp has accepted the information signal, the signal stored in the element Vkp 1 located below it can be erased, so that it is now ready to receive a new unit of information. The output signal Xkp from Vkp is firstly transmitted onwards to input I of Vkp 1 and at the same time transmitted to one of the erasure inputs, for example N1 of Vkp 1. The last element Vkp of a gating group transmits its output signal Xkp onwards to the system to be controlled, and consequently initiates an operating procedure k. After the operating procedure has been terminated, the signal Xkp is erased from the system under control via an erasure input of Vkp generated by means of an indication R1.: sent in reply.

The output signals Xkp are finally transmitted onwards as cut-off signals to the erasure inputs of the elements of other gating groups. The operations of the cutoff signals are described in detail hereinafter.

Each output signal Xkp of any gate element therefore possesses three functions:

(1) Transmission onwards of the information signal to the element Vkp (or, where applicable, to the system to be controlled).

(2) Erasure of the element Vkp 1.

(3) Emission of cut-off signals to the gate elements of other gating groups.

Corresponding considerations apply to the conditional outputs Y, Z, Y, 'Z1 FIGURE 3 shows the general cir-- cuit diagram of gating group k when P=4.

In the gating group illustrated here, there is a prior switching of an erasure-dominating storage device possessing the following function:

From a central control point or from a system which is to be controlled there arrives the indication Ik that the conditions have been fulfilled for the initiation of the control procedure k. This signal is called the readiness signal for operating procedure k. In order that no information should get lost through the erasing effect of cut-off signals, this information is stored in the storage device mentioned, which should be designated input storage device Ek, until the succeeding gate element Vkl has taken the signal over. The output signal Xkl then erases Ek, so that the latter is now ready to accept fresh signals. All the input storage devices Ek are combined in priority level O. The readiness signal, when it has vacated the input storage device, extends through to the last priority level not yet cut-oir. Here it waits until the cutting-oir of the blocked level has been cancelled, and then it proceeds further. If the signal has arrived at the last priority level P, then the control procedure is initiated by Xkp.

From the very large number of possibilities that exist as regards connecting up gate circuits, only some characteristic examples will now be selected:

(l) The simplest gating control system consists of two gating groups k 1, 2 and of the priorities 11:0, 1. The output signal of each of the gate elements is conducted to the erasure input of the other element (EITHER-OR control). The control procedure which is the first to rereceive the readiness signal is the first to take place. When, however, the conditional signal Ykl is employed in place of the output signal Xkl, then the iirst control procedure to occur is the one at which the readiness signal and the conditioning signal Sy rst arrive simultaneously. If an action involving cutting-off is to be instituted only when a signal SZ appears as the expression of a condition, then the control procedure k will be initiated via the output Xkl, and the lines associated with the cut-off action will be led from the outputs Zk, to the erasure inputs N of the adjacent element (conditional cut-olf).

(2) If the switching system possesses, in place of two gating groups, a plurality of these (k=l, 2, 3 K), then by this means it is possible, for instance to control a hydraulic longwall support arrangement made up of several self-advancing roof support units. The output signal of a gating group Vm initiates the advance procedure of an associated unit and is, in addition, conducted to the erasure inputs of an optional number of adjacent groups, of which each for its part is associated with a roof support unit. Then several units will not be able to advance simultaneously.

If the units are to advance at shorter intervals, then the number of actions involving cutting-off effected by a gating group must in certain circumstances be altered during operation. To this end, the lines corresponding to the type of cut-off with the lesser number must be led from Xkl to the erasure inputs of the adjacent elements to be cut olf, and the cut-offs still lacking must be led away via the conditional output Zkl. If the condition Sz is not present, the cut-olf type with the lesser number is effective; if the signal Sz is present, then the cut-offs selected by Z have to be included in addition.

(3) If some roof support units are to advance preferentially, possibly with the aim of aligning the conveyor, a further priority level has to be inserted, i.e. p=0, 1, 2. The level p=2 which emits the control signals is switched in this instance in the same manner as was described in the preceding section. At the level p=1 only those cut-off lines are connected that run from the gate elements of the preferred frames. If a preferred readiness signal arrives, it can in any event extend through unhindered to level 1 and erase all the adjacent signals of level 1 which are waiting within its cut-off domain. If at this time one of the adjacent frames is already making an advance, the signal waits on level 1 until, upon the termination of the advancing action, level 2 is erased and then for its part initiates its own control procedure. Such adjacent signals as are produced must wait until the level p=1 is indicated to be clear.

(4) A further example is the safeguarding of branchtracks in the case of systems of railway points. This demands control of the sequence of switching operations in clearing for trafc the tracks which are in competition with each other. Clearances should generally take place according to the time sequence for the arrival of the trains. The number P of the priority level must in this respect be equal to the number of competing tracks. Each element cuts off all other elements of the same level. The readiness signal that first arrives extends directly through to level -P and releases the appropriate track'for traflic. If meanwhile further announcements of impending arrivals come in, then they can extend through in the sequence of their arrival up to the level p-1, p-2, etc., and at their level can cut off all other elements. If the train has left the system of points, then the control signal is erased, and this level P is cleared. The signal waiting on P-l extends through to P, so that the next track becomes clear, and in addition each signal waiting on a lower level moves up to the next higher priority level.

(5) When a gating system is applied to belt conveyors, the negativing outputs Y, 'Z' are utilized. Let it be assumed that every following belt is only intended to start up when the belt that was previously switched on is already running. In the case of a motionless belt, the negativing outputs will then emit a signal which will be transmitted to an erasure input of the gating group of the following belt. By this means, all the following belts are blocked. Only when the previous belt is running and the negativing outputs are carrying no signal, is the following belt able to start up. By utilizing the conditional outputs Y, Z, the starting up of the =belt can also be made dependent upon further conditions.

(6) In all the hereinbefore described gate circuits the presupposition was made that every element erases the preceding element of the same gating group and that the cut-olf lines proceeding from one element lead to elements of the same priority level. If either one or both these conditions are renounced, then a further category of cut-off conditions with a more complicated logic can be derived.

The gate elements employed in the circuits described are, as is immediately obvious from the above explanation, formed identically to each other, and they constiute in themselves basic blocks of any desired switching system. For use in mines basic blocks of pneumatic switching systems are recommended, because such pneumatic switching systems, in contrast to electrical switching systems, do not necessitate any special measures to obviate the danger of explosion.

The circuits described above are clearly only examples. From the general viewpoint, circuits according to the invention may be employed in central control units for process regulating devices when definite conditions regarding cutting-olf actions are present in a system of automatic machines linked with each other (Whatever its complexity) I claim:

1. In a logical switching system, a gate unit comprislng:

a storage device consisting of logic elements which afford the storage device two inputs, namely an information input and an erasure input of which the latter dominates in the event of coincident signals, and two outputs one of which feeds out a signal fed to the information input, which signal is also stored until erased by a signal fed to the erasure input, the other output always being opposite to the rst output, said outputs thereby being unconditional;

an OR element connected in front of the erasure input of the storage device to provide for erasure from a plurality of erasure signal sources; and

two AND elements each connected at one of its inputs to one output of the storage device, thereby to provide four outputs additional to the said two unconditional outputs, said four additional outputs being conditional, in dependence on signals fed to the other input of said AND element.

2. A gate unit according to claim 1, wherein each storage device comprises two OR elements one of which has one of its inputs connected to the output of the second and its output connected by a feed-back line to one of the inputs of the second, the other two inputs of the OR elements respectively constituting the said information input and the erasure input and the two outputs constituting the said two unconditional outputs.

3. A gate unit according to claim 1, formed as a unitary block or module.

S y 4. A gate unit according to claim 1, adapted for pneumatic operation.

5. In a mine working having a self-advancing pit prop support system, a logical switching system for controlling advance of the pit props selectively, said switching system comprlsing:

a plurality of similar gate units each comprising an erasure dominating storage device, an OR element connected in front of the erasure input of said storage device and two AND elements connected to each output of said storage device to provide for conditional outputs in addition to two unconditional outputs;

an information line for feeding signals to one input of each storage device;

erasure lines for feeding erasure signals to the OR element in front of each storage device, including lines connecting the gate units; and

control lines for feeding output signals for the gate units to the pit prop control means.

References Cited UNITED STATES PATENTS 3,285,015 11/1966 Carnegie et al. 61-45 3,392,531 7/1968 Bodo-Werner Ratz 61-45 3,392,532 7/1968 Jacobi 61--45 3,434,389 3/1969 Grisebach 91-36 FOREIGN PATENTS 1,459,372 10/1966 France.

DENNIS L. TAYLOR, Primary Examiner 

